Ultra-High Temperature Operated Ni-Rich Cathode Stabilized by Thermal Barrier for High-Energy Lithium-Ion Batteries.

The pursuit of high energy density batteries has expedited the fast development of Ni-rich cathodes. However, the chemo-mechanical degradation induced by local thermal accumulation and anisotropic lattice strain is posing great obstacles for its wide applications. Herein, a highly-antioxidative BaZrO3 thermal barrier engineered LiNi0.8Co0.1Mn0.1O2 cathode through an in situ construction strategy is first reported to circumvent the above issues. It is found that the Zr ions are incorporated to Ni-rich material lattice and influence on the topotactic lithiation as well as enhance the oxygen electronegativity through the rigid Zr─O bonds, which effectively alleviates the lattice strain propagation and decreases the excessive oxidization of lattice oxygen for charge compensation. More importantly, the BaZrO3 thermal barrier with an ultra-low thermal conductivity validly impedes the fast heat exchange between electrode and electrolyte to mitigate the severe surface side reactions. This helps an ultra-high mass loading Li-ion pouch cell deliver a specific energy density of 690 Wh kg-1 at active material level and an excellent capacity retention of 92.5% after 1400 cycles under 1 C at 25 °C. Tested at a high temperature of 55 °C, the pouch type full-cell also exhibits 88.7% in capacity retention after 1200 cycles.

Defective oxygen inert phase stabilized high-voltage nickel-rich cathode for high-energy lithium-ion batteries.

Pushing layered cathode to higher operating voltage can facilitate the realization of high-energy lithium-ion batteries. However, the released oxygen species initiate materials surface upon highly delithiated states will react severely with electrolyte, accelerating the structure deterioration and triggering the thermal degradation. Here we propose an inert phase of La2Mo2O9 with abundant oxygen vacancies (about 41%) by regulating the annealing temperature to engineer the cathode interface beyond conventional modifications. By employing LiNi0.8Co0.1Mn0.1O2 as a model system and extending to higher voltage-operated LiCoO2 and Li-rich cathode, we demonstrate that the introduced lanthanum and molybdenum ions will transfer electrons to enhance the surface oxygen electronegativities, thus served as "oxygen anchor" to alleviate oxygen evolution. Furthermore, the possible released oxygen can be operando captured and reserved by ß-phase La2Mo2O9 depositor for the intrinsic high oxygen vacancy formation energy. The reaction involving oxygen species with electrolyte is fundamentally diminished, thus effectively mitigate the structure deterioration and elevate the electrochemical performances, enabling a 1.5-Ah pouch-type full cell to exhibit negligible 6.0% capacity loss after 400 cycles.

Surface Coupling between Mechanical and Electric Fields Empowering Ni-Rich Cathodes with Superior Cyclabilities for Lithium-Ion Batteries.

Ni-rich cathodes with high energy densities are considered as promising candidates for advanced lithium-ion batteries, whereas their commercial application is in dilemma due to dramatic capacity decay and poor structure stability stemmed from interfacial instability, structural degradation, and stress-strain accumulation, as well as intergranular cracks. Herein, a piezoelectric LiTaO3 (LTO) layer is facilely deposited onto Li[Nix Coy Mn1- x - y ]O2 (x = 0.6, 0.8) cathodes to induce surface polarized electric fields via the intrinsic stress-strain of Ni-rich active materials, thus modulating interfacial Li+ kinetics upon cycling. Various characterizations indicate that the electrochemical performances of LTO-modified cathodes are obviously enhanced even under large current density and elevated temperature. Intensive explorations from in situ X-ray diffraction technique, finite element analysis, and first-principle calculation manifest that the improvement mechanism of LTO decoration can be attributed to the enhanced structural stability of bulk material, suppressed stress accumulation, and regulated ion transportation. These findings provide deep insight into surface coupling strategy between mechanical and electric fields to regulate the interfacial Li+ kinetics behavior and enhance structure stability for Ni-rich cathodes, which will also arouse great interest from scientists and engineers in multifunctional surface engineering for electrochemical systems.